With the development of the display technologies, touch screens have found wide application. Currently, depending on their working principles, the touch screens can be categorized into resistive-sensing touch screens, capacitive-sensing touch screens, optical-sensing touch screens, and so forth. In accordance with their structures, the touch screens can be classified into on-cell touch screens, in-cell touch screens, and so on. The in-cell touch screens have an advantage of a thinned thickness and reduced cost.
Existing optical touch screen technology provides a touch sensing mechanism that is based on detection of ambient light. For example, photosensitive transistors are integrated in the pixels of a liquid crystal display panel to detect the external ambient light. As the photosensitive transistors are embedded in the array substrate of the liquid crystal display panel, an in-cell optical touch screen is implemented. This in-cell optical touch screen typically requires complicated fabricate processes.